JoeR Posted December 6, 2011 Report Share Posted December 6, 2011 So occasionally when I am driving, I hear a clicking sound coming from under the passenger side dash near the door, and a couple seconds after that, the engine will loose power and die. I know that both the auto choke relay as well as the fuel pump control unit are located there. Would these be the problem? Has anyone else had this problem? Quote Link to comment
datzenmike Posted December 7, 2011 Report Share Posted December 7, 2011 If there is a problem with the alternator charge the choke heater relay will buzz sometimes. But this won't cause the engine to quit. The fuel pump relay on the other hand has to be working to keep the pump... pumping. In operation, turning the key to ON will turn the relay on and start the fuel pump but there is a timer of 20-30 seconds? and will then shut off. Turning the key to START will also turn the relay on and as long as you are cranking the pump will operate but when the key is released the timer begins again. The relay will stay on only if there is oil pressure and charge from the alternator which it is assumed the motor has started and is running. Why the pump relay? Well after an accident, do you really want the pump to continue supplying gas to a broken fuel line or carburetor untill the tank is empty while you lay there unconscious? If you suspect a faulty relay forget the manuals, many don't even mention it. I did find this very helpful site for fixing it yourself and saving $50. http://dlarson.hubpages.com/hub/The-Datsun-and-Nissan-Pickup-Fuel-Pump-Relay-What-the-Haynes-Automotive-Repair-Manual-Wont-Tell-You. Quote Link to comment
ggzilla Posted December 7, 2011 Report Share Posted December 7, 2011 Hey that's a great article, with photos and every thing. Another reason why everyone should have the Nissan factory service manual, instead of getting a 3rd-party manual (Chilton, Haynes, etc). Quote Link to comment
datzenmike Posted December 7, 2011 Report Share Posted December 7, 2011 My '74 FSM mentions it and shows the wiring and inputs but no circuit diagram and it's not in the wiring diagram... go figure. Quote Link to comment
JoeR Posted December 8, 2011 Author Report Share Posted December 8, 2011 Thanks for the link to that article, I will be checking that out in the next few days. It's funny how the Haynes manual doesn't mention the fuel pump relay. I have a Chilton manual and it doesn't show anything about a fuel pump relay either. But I I have one more question: can the problem be exacerbated by there being more fuel in the tank? I seem to only have the problem when the tank is more that half full. Quote Link to comment
datzenmike Posted December 8, 2011 Report Share Posted December 8, 2011 No, the pump doesn't know what's in the tank and the relay knows even less. Quote Link to comment
JoeR Posted December 12, 2011 Author Report Share Posted December 12, 2011 Once again, thanks for sharing that info. Any tips of checking the fuel pump to see if thats not the problem? Quote Link to comment
datzenmike Posted December 12, 2011 Report Share Posted December 12, 2011 Well if you disconnect the plug from the relay and make a jumper wire from the White (ignition) to the White/Black (pump) the pump should only run when the key is in the ON position. If it runs without quitting, then the relay or one of the other inputs is bad causing it to shut off. If the pump still acts up then it could be the pump as you've eliminated the relay by jumpering around it.. . Quote Link to comment
ggzilla Posted December 12, 2011 Report Share Posted December 12, 2011 Do the standard fuel pump 1) Volume and 2) Pressure tests. The pressure and volume and similar for all Datsuns. Note that the 720 electric fuel pumps have filters inside the pump. If they never been changed, it can affect the volume and the pressure. New filters are available from Nissan. The pump is just in front the rear left wheel on the frame. Quote Link to comment
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